Led and phosphor combinations for high luminous efficacy lighting with superior color control

ABSTRACT

A light emitting device comprises a first group of one or more LEDs each configured to emit light having a blue color point in the 1931 CIE x,y Chromaticity Diagram, a second group of one or more LEDs each configured to emit light having a cyan or yellow color point in the 1931 CIE x,y Chromaticity Diagram, and a third group of one or more LEDs each configured to emit light having a red color point in the 1931 CIE x,y Chromaticity Diagram.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/431,094 filed on Jun. 4, 2019, which claims benefit of priority toU.S. Provisional Patent Application No. 62/680,918 titled “LED ANDPHOSPHOR COMBINATIONS FOR HIGH LUMINOUS EFFICACY LIGHTING WITH SUPERIORCOLOR CONTROL” and filed Jun. 5, 2018. Each of the foregoingapplications is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This disclosure generally relates to combinations of phosphors and lightemitting diodes having high luminous efficacy and improved colorcontrol.

BACKGROUND

Material systems for semiconductor light-emitting diodes andsemiconductor laser diodes (both referred to herein as LEDs) includeGroup III-V semiconductors, particularly binary, ternary, and quaternaryalloys of gallium, aluminum, indium, and nitrogen, also referred to asIII-nitride materials. LEDs are often combined with a wavelengthconverting material such as a phosphor. An LED combined with one or morewavelength converting materials may be used to create white light ormonochromatic light of other colors. All or only a portion of the lightemitted by the LED may be converted by the wavelength convertingmaterial. Unconverted light may be part of the final spectrum of light,though it need not be. Examples of common devices include ablue-emitting LED combined with a yellow-emitting phosphor, ablue-emitting LED combined with cyan- and red-emitting phosphors, aUV-emitting LED combined with blue- and yellow-emitting phosphors, and aUV-emitting LED combined with blue-, cyan-, and red-emitting phosphors.The term “phosphor” is used herein to refer to any wavelength convertingmaterial, including but not limited to inorganic phosphor compounds.

In commercial applications, manufactured LED dice (L0) are packaged(L1), combined on a carrier (L2), and fitted into a module (L3) that caninclude drivers, controls, and sensors. Multiple L3 modules can be usedin lamps or luminaires (L4) that in turn can be part of a complete homeor commercial lighting system (L5).

A color point is a point in a chromaticity diagram characterizing aparticular spectrum of light as a color perceived by a human with normalcolor vision. A correlated color temperature is the temperaturecorresponding to the point on the blackbody curve in a chromaticitydiagram to which a color point is most closely correlated.

Light emitted by several differently colored direct emitting LEDs (e.g.,semiconductor diode structures that directly emit blue, cyan, and redlight) may be combined to provide white light having a desired colorpoint and correlated color temperature. Alternatively, light emitted byone or more phosphor converted LEDs (e.g. a blue emitting LED excitingone or more phosphors) may individually or in combination provide whitelight having a desired color point and correlated color temperature. Oneor more direct emitting LEDs may be combined with light emitted by oneor more phosphor converted LEDs to provide white light with a desiredcolor point or correlated color temperature.

Combining multiple phosphors with a single blue emitting LED can resultin interactions between the phosphors, for example absorption by onephosphor of light emitted by another, that reduces the efficiency of thedevice. Combining light emitted by direct emitting LEDs or by phosphorconverted LEDS to make white light of a desired color point may also beinefficient if the desired white light color point is far from the colorpoints of the light emission from the individual LEDs. Further,combining light emitted by (e.g., red) direct emitting LEDs with lightemitted by phosphor converted LEDs may be difficult in practice as aresult of differing drive current and temperature dependent behavior ofthe different LEDs.

SUMMARY

In one aspect of the invention, a light emitting device comprises afirst group of one or more LEDs each configured to emit light having ablue color point in the 1931 CIE x,y Chromaticity Diagram, a secondgroup of one or more LEDs each configured to emit light having a cyan oryellow color point in the 1931 CIE x,y Chromaticity Diagram, and a thirdgroup of one or more LEDs each configured to emit light having a redcolor point in the 1931 CIE x,y Chromaticity Diagram.

The first group of LEDs, the second group of LEDS, and the third groupof LEDs are arranged to combine light emitted by the LEDs to form awhite light output from the light emitting device. One or more of theprimaries (blue color point, cyan or yellow color point, and red colorpoint) may be desaturated, that is, distant from the monochromatic locusidentifying monochromatic light in the chromaticity diagram.Desaturation moves the primary color points closer to the desired colorpoint of the white light output, improving efficiency of the lightemitting device, but as a trade-off reduces the gamut area of thechromaticity diagram spanned by the primaries and thereby reduces colortunability of the output of the light emitting device.

Some or all of the LEDs may be phosphor converted LEDs in whichwavelength converting material partially or entirely converts blue lightemitted by a semiconductor diode structure to light of a longerwavelength. The blue light emitted by the semiconductor diode structuresmay have a peak wavelength in the range of 430 nm to 475 nm, forexample. Alternatively some of the LEDs may be direct emitting LEDs andothers of the LEDs phosphor converted LEDs.

The output of the light emitting device may optionally be tuned byvarying drive current to one or more of the LEDs, e.g., to one or moreof the groups of LEDs.

In some embodiments, the first group has an average 1931 CIE x,y colorpoint of x_(blue), y_(blue), the second group has an average 1931 CIEx,y color point of x_(yellow-cyan), y_(yellow-cyan), and the third grouphas an average 1931 CIE x,y color point of x_(red), y_(red),1.10≤(x_(blue)+x_(yellow-cyan)+x_(red))≤1.40,1.05≤(y_(blue)+y_(yellow-cyan)+y_(red))≤1.25, each of the LEDs in thefirst, second, and third groups has a color point for which the x valuein the 1931 CIE x,y Chromaticity Diagram is greater than 0.15, and eachof the LEDs in the first, second, and third groups has a color point forwhich the y value in the 1931 CIE x,y Chromaticity Diagram is greaterthan 0.15.

In some embodiments, 1.15≤(x_(blue)+x_(yellow-cyan)+x_(red))≤1.40,1.10≤(y_(blue)+y_(yellow-cyan)+y_(red))≤1.25, each of the LEDs in thefirst, second, and third groups has a color point for which the x valuein the 1931 CIE x,y Chromaticity Diagram is greater than 0.2, and eachof the LEDs in the first, second, and third groups has a color point forwhich the y value in the 1931 CIE x,y Chromaticity Diagram is greaterthan 0.2.

In some embodiments, 1.20<(x_(blue)+x_(yellow-cyan)+x_(red))≤1.32,1.10≤(y_(blue)+y_(yellow-cyan)+y_(red))≤1.20, each of the LEDs in thefirst, second, and third groups has a color point for which the x valuein the 1931 CIE x,y Chromaticity Diagram is greater than 0.2, and eachof the LEDs in the first, second, and third groups has a color point forwhich the y value in the 1931 CIE x,y Chromaticity Diagram is greaterthan 0.2.

The color points (x_(blue), y_(blue)), (x_(yellow-cyan),y_(yellow-cyan)), and (x_(red), y_(red)) of the primaries may span anabsolute gamut in the CIE 1931 x,y Chromaticity Diagram of, for example,0.01<gamut area<0.07, preferably 0.015<gamut area<0.055 and mostpreferred 0.02<gamut area<0.045.

In some embodiments, the LEDs of the first group each comprise asemiconductor diode structure configured to emit blue light and a firstphosphor arranged to absorb blue light emitted by the semiconductordiode structure and in response emit light of a longer wavelength mixedwith unabsorbed blue light, and the LEDs of the second group eachcomprise a semiconductor diode structure configured to emit blue lightand a second phosphor arranged to absorb blue light emitted by thesemiconductor diode structure and in response emit light of a longerwavelength. The LEDs of the third group each comprise a semiconductordiode structure configured to emit blue light, the first phosphorarranged to absorb blue light emitted by the semiconductor diodestructure and in response emit light of a longer wavelength, and thesecond phosphor arranged to absorb blue light emitted by thesemiconductor diode structure and in response emit light of a longerwavelength. The first phosphor may for example absorb blue light andemit red light, and the second phosphor absorb blue light and emit cyanlight.

These and other embodiments, features and advantages of the presentinvention will become more apparent to those skilled in the art whentaken with reference to the following more detailed description of theinvention in conjunction with the accompanying drawings that are firstbriefly described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a table summarizing color characteristics of 4 example lightemitting devices (Examples 1-4) discussed below, FIG. 1B is a tablesummarizing color characteristics of another 5 example light emittingdevices (Examples 5-9) discussed below, and FIG. 1C is a tablesummarizing additional color characteristics of Examples 1-9.

FIG. 2A, FIG. 2B, FIG. 2C, FIG. 2D, and FIG. 2E illustrate,respectively, a graph showing blue, cyan-yellow, and red color pointsand the Planckian locus, a graph of spectral power versus wavelength, agraph with current versus correlated color temperature (CCT), a graph offlux versus correlated color temperature, and a graph of color renderingindex (CRI_Ra/R9) versus correlated color temperature for the lightemitting device of Example 1. FIG. 2F shows a table presentingadditional characteristics of the example light emitting device.

FIG. 3A, FIG. 3B, FIG. 3C, FIG. 3D, and FIG. 3E illustrate,respectively, a graph showing blue, cyan-yellow, and red color pointsand the Planckian locus, a graph of spectral power versus wavelength, agraph with current versus correlated color temperature (CCT), a graph offlux versus correlated color temperature, and a graph of color renderingindex (CRI_Ra/R9) versus correlated color temperature for the lightemitting device of Example 2. FIG. 3F shows a table presentingadditional characteristics of the example light emitting device.

FIG. 4A, FIG. 4B, FIG. 4C, FIG. 4D, and FIG. 4E illustrate,respectively, a graph showing blue, cyan-yellow, and red color pointsand the Planckian locus, a graph of spectral power versus wavelength, agraph with current versus correlated color temperature (CCT), a graph offlux versus correlated color temperature, and a graph of color renderingindex (CRI_Ra/R9) versus correlated color temperature for the lightemitting device of Example 3. FIG. 4F shows a table presentingadditional characteristics of the example light emitting device.

FIG. 5A, FIG. 5B, FIG. 5C, FIG. 5D, and FIG. 5E illustrate,respectively, a graph showing blue, cyan-yellow, and red color pointsand the Planckian locus, a graph of spectral power versus wavelength, agraph with current versus correlated color temperature (CCT), a graph offlux versus correlated color temperature, and a graph of color renderingindex (CRI_Ra/R9) versus correlated color temperature for the lightemitting device of Example 4. FIG. 5F shows a table presentingadditional characteristics of the example light emitting device.

FIG. 6A, FIG. 6B, FIG. 6C, FIG. 6D, and FIG. 6E illustrate,respectively, a graph showing blue, cyan-yellow, and red color pointsand the Planckian locus, a graph of spectral power versus wavelength, agraph with current versus correlated color temperature (CCT), a graph offlux versus correlated color temperature, and a graph of color renderingindex (CRI_Ra/R9) versus correlated color temperature for the lightemitting device of Example 5. FIG. 6F shows a table presentingadditional characteristics of the example light emitting device.

FIG. 7A, FIG. 7B, FIG. 7C, FIG. 7D, and FIG. 7E illustrate,respectively, a graph showing blue, cyan-yellow, and red color pointsand the Planckian locus, a graph of spectral power versus wavelength, agraph with current versus correlated color temperature (CCT), a graph offlux versus correlated color temperature, and a graph of color renderingindex (CRI_Ra/R9) versus correlated color temperature for the lightemitting device of Example 6 described below. FIG. 7F shows a tablepresenting additional characteristics of the example light emittingdevice.

FIG. 8A, FIG. 8B, FIG. 8C, FIG. 8D, and FIG. 8E illustrate,respectively, a graph showing blue, cyan-yellow, and red color pointsand the Planckian locus, a graph of spectral power versus wavelength, agraph with current versus correlated color temperature (CCT), a graph offlux versus correlated color temperature, and a graph of color renderingindex (CRI_Ra/R9) versus correlated color temperature for the lightemitting device of Example 7 described below. FIG. 8F shows a tablepresenting additional characteristics of the example light emittingdevice.

DETAILED DESCRIPTION

The detailed description illustrates by way of example, not by way oflimitation, the principles of the invention. This description describesseveral embodiments, adaptations, variations, alternatives and uses ofthe invention, including what is presently believed to be the best modeof carrying out the invention.

As summarized above, the light emitting devices disclosed hereincomprise a first group of one or more LEDs each configured to emit lighthaving a blue color point in the 1931 CIE x,y Chromaticity Diagram, asecond group of one or more LEDs each configured to emit light having acyan or yellow color point in the 1931 CIE x,y Chromaticity Diagram, anda third group of one or more LEDs each configured to emit light having ared color point in the 1931 CIE x,y Chromaticity Diagram.

The tables of FIGS. 1A-1B show nine examples for combinations of thethree color points of these devices that satisfy the requirementsummarized above that the first group has an average 1931 CIE x,y colorpoint of x_(blue), y_(blue), the second group has an average 1931 CIEx,y color point of x_(yellow-cyan), y_(yellow-cyan), and the third grouphas an average 1931 CIE x,y color point of x_(red), y_(red),1.10≤(x_(blue)+x_(yellow-cyan)+x_(red))≤1.40,1.05≤(y_(blue)+y_(yellow-cyan)+y_(red))≤1.25, each of the LEDs in thefirst, second, and third groups has a color point for which the x valuein the 1931 CIE x,y Chromaticity Diagram is greater than 0.15, and eachof the LEDs in the first, second, and third groups has a color point forwhich the y value in the 1931 CIE x,y Chromaticity Diagram is greaterthan 0.15.

Subsets of Examples 1-9 satisfy the requirement summarized above that1.15≤(x_(blue)+x_(yellow-cyan)+x_(red))≤1.40,1.10≤(y_(blue)+y_(yellow-cyan)+y_(red))≤1.25, each of the LEDs in thefirst, second, and third groups has a color point for which the x valuein the 1931 CIE x,y Chromaticity Diagram is greater than 0.2, and eachof the LEDs in the first, second, and third groups has a color point forwhich the y value in the 1931 CIE x,y Chromaticity Diagram is greaterthan 0.2.

Subsets of Examples 1-9 satisfy the requirement summarized above that1.20<(x_(blue)+x_(yellow-cyan)+x_(red))≤1.32,1.10≤(y_(blue)+y_(yellow-cyan)+y_(red))≤1.20, each of the LEDs in thefirst, second, and third groups has a color point for which the x valuein the 1931 CIE x,y Chromaticity Diagram is greater than 0.2, and eachof the LEDs in the first, second, and third groups has a color point forwhich the y value in the 1931 CIE x,y Chromaticity Diagram is greaterthan 0.2.

As shown in the tables of FIGS. 1A-1C, the color points (x_(blue),y_(blue)), (x_(yellow-cyan), y_(yellow-cyan)), and (x_(red), y_(red)) ofthe primaries may span an absolute gamut in the CIE 1931 x,yChromaticity Diagram of, for example, 0.01<gamut area<0.07, preferably0.015<gamut area<0.055 and most preferred 0.02<gamut area<0.045.

In the tables of FIGS. 1A-1B, R CP, Y CP, and B CP refer respectively tothe red color point, the cyan or yellow color point, and the blue colorpoint. Any of these color points may be generated using one or moreLEDs, for example one or more phosphor-converted LEDs. The color pointsshown in the tables of FIGS. 1A-1B are averages of color points within agroup of LEDs (i.e., within the first, second, or third groups referredto above). The LEDs for a particular group form a color box in achromaticity diagram, with the average color point for the group fallingwithin the color box. The table of FIG. 1C shows, for each of Examples1-9, the minimum and maximum values for(x_(blue)+x_(yellow-cyan)+x_(red)), the minimum and maximum values for(y_(blue)+y_(yellow-cyan)+y_(red)), the minimum and maximum values ofgamut area, and the average (center value) of gamut area.

Typically all of the LEDs in the first group of LEDs are phosphorconverted LEDs having the same configuration; all of the LEDs in thesecond group of LEDS are phosphor converted LEDS having the sameconfiguration, but different from that of the first group; and all ofthe phosphor converted LEDS in the third group are phosphor convertedLEDS having the same configuration, but different from that of the firstand second groups. Typically all of these phosphor converted LEDconfigurations comprise a semiconductor diode structure configured toemit blue light, and one or more phosphors that absorb the blue lightand in response emit light of a longer wavelength.

The LEDs of the first, second, and third groups may produce desaturatedoutput light as a result of phosphor emission combining with unabsorbedblue light from the semiconductor diode structure, or as a result of thespectral breadth of emission from the phosphor, or for both reasons.Typically, the output from the LEDs in the first group is a desaturatedbluish white, with about 50% of the blue light emitted from asemiconductor diode structure converted by a phosphor to a longerwavelength (for example, to a red wavelength).

As noted above in the background section, conventional devices maycombine multiple phosphors with a single blue emitting diode to generatea desired white light output directly, with each phosphor converted LEDproducing essentially the same output. In contrast, in the lightemitting devices disclosed herein the phosphors used to generate adesired (for example, white) light output are distributed among three ormore groups of LEDS, with the different groups emitting light atdifferent color points, such that the combined emission from the threedifferent groups provides the desired (e.g., white) light output.

In some embodiments in which two different phosphors are distributedamong three groups of LEDS, the distribution of phosphors can bedescribed as:

LED  group  1 = blue  die + a * phosphor  1;LED  group  2 = blue  die + b * phosphor  2; andLED  group  3 = blue  die + c * phosphor  1 + d * phosphor  2;

where the coefficients a, b, c, and d abstractly indicate the amount ofthe indicated phosphor used. These coefficients may be selected suchthat the phosphor absorbs and converts a desired fraction (up to 100%)of the blue semiconductor diode emission to phosphor emission.

The LEDs will together give a color point and flux, which can bedescribed in CIE1931 color space with coordinates (X,Y,Z), where Y isequal to the luminous flux, and the color point (x,y) is then derived asx=X/(X+Y+Z) and y=Y/(X+Y+Z). The X,Y,Z coordinates will be function ofthe blue die wavelength λ, and the phosphor loading (a,b,c,d).

With the system being defined by (λ, a,b,c,d), there are three degreesof freedom, which can be used to adjust the flux Y, color rendering, andfor example, also adjust the flux value at another color point (with adifferent driving ratio). In effect, in such embodiments the lightemitting device includes one LED for each desired phosphor, plus one“remainder” LED. The color points of the LEDs may be selected such thatthe sum of the luminous flux at the desired color point and colorrendering requirement is maximized. The luminous efficacy willpredominantly be a function of the amount of phosphor (loading ratio).

In one embodiment, phosphor 1 absorbs blue light and emits red light,and phosphor 2 absorbs blue light and emits cyan light.

Given the guidance provided in this specification as to desired colorpoints for the disclosed light emitting devices, one of ordinary skillin the art can choose suitable phosphor materials to combine with blueemitting LEDs to construct the disclosed devices. Generally, anysuitable phosphor or wavelength converting materials may be used. Forexample, a predominantly white-emitting LED could result from pairing ablue-emitting LED with a wavelength converting material such asY₃Al₅O₁₂:Ce³⁺ that absorbs some of the blue light and emits yellowlight. Other examples of phosphors that may be used include aluminumgarnet phosphors with the general formula(Lu_(1−x−y−a−b)Y_(x)Gd_(y))₃(Al_(1−z)Ga_(z))₅O₁₂:Ce_(a)Pr_(b) wherein0<x<1, 0<y<1, 0<z≤0.1, 0<a≤0.2 and 0<b≤0.1, such as Lu₃Al₅O₁₂:Ce³⁺ andY₃Al₅O₁₂:Ce³⁺ which emit light in the yellow-cyan range; and(Sr_(1−x−y)Ba_(x)Ca_(y))_(2−z)Si_(5−a)Al_(a)N_(8−a)O_(a):Eu_(z) ²⁺wherein 0≤a<5, 0<x≤1, 0≤y≤1, and 0<z≤1, such as Sr₂Si₅N₈:Eu²⁺, whichemit light in the red range. Other cyan, yellow, and red emittingphosphors may also be suitable, including(Sr_(1−a−b)Ca_(b)Ba_(c))Si_(x)N_(y)O_(z):Eu_(a) ²⁺ (a=0.002-0.2,b=0.0-0.25, c=0.0-0.25, x=1.5-2.5, y=1.5-2.5, z=1.5-2.5) including, forexample, SrSi₂N₂O₂:Eu²⁺;(Sr_(1−u−v−x)Mg_(u)Ca_(v)Ba_(x))(Ga_(2−y−z)Al_(y)In_(z)S₄):Eu²⁺including, for example, SrGa₂S₄:Eu²⁺; Sr_(1−x)Ba_(x)SiO₄:Eu²⁺; and(Ca_(1−x)Sr_(x))S:Eu²⁺ wherein 0<x<1 including, for example, CaS:Eu²⁺and SrS:Eu²⁺. Examples of suitable yellow/cyan emitting phosphorsinclude but are not limited to Lu_(3−x−y)M^(y)Al_(5−z)A_(z)O₁₂:Ce_(x)where M=Y, Gd, Tb, Pr, Sm, Dy; A=Ga, Sc; and (0<x≤0.2);Ca_(3−x−y)M^(y)Sc_(2−z)A_(z)Si₃O₁₂:Ce_(x) where M=Y, Lu; A=Mg, Ga; and(0<x≤0.2); Ba_(1−x−y)M_(y)SiO₄:Eu_(x) where M=Sr, Ca, Mg and (0<x≤0.2);Ba_(2−x−y−z)M_(y)K_(z)Si_(1−z)P_(z)O₄Eu_(x) where M=Sr, Ca, Mg and(0<x≤0.2); Sr_(1−x−y)M_(y)Al_(2−z)Si_(z)O_(4−z)N_(z):Eu_(x) where M=Ba,Ca, Mg and (0<x≤0.2); M_(1−x)Si₂O₂N₂:Eu_(x) where M=Sr, Ba, Ca, Mg and(0<x≤0.2); M_(3−x)Si₆O₉N₄:Eu_(x) where M=Sr, Ba, Ca, Mg and (0<x≤0.2);M_(3−x)Si₆O₁₂N₂:Eu_(x) where M=Sr, Ba, Ca, Mg and (0<x≤0.2);Sr_(1−x−y)M_(y)Ga_(2−z)Al_(z)S₄:Eu_(x) where M=Ba, Ca, Mg and (0<x≤0.2);Ca_(1−x−y−z)M_(z)S:Ce_(x)A_(y) where M=Ba, Sr, Mg; A=K, Na, Li; and(0<x≤0.2); Sr_(1−x−z)M_(z)Al_(1+y)So_(4.2−y)N_(7−y)O_(0.4+y):Eu_(x)where M=Ba, Ca, Mg and (0<x≤0.2); Ca_(1−x−y−z) M_(y)Sc2O4:CexAz whereM=Ba, Sr, Mg; A=K, Na, Li; and (0<x≤0.2);Mx−zSi6_(−y−2x)Al_(y+2x)O_(y)N_(8−y):Eu_(z) where M=Ca, Sr, Mg and(0<x≤0.2); and Ca_(8−x−y)M_(y)MgSiO₄Cl₂:Eu_(x) where M=Sr, Ba and(0<x≤0.2). Examples of suitable red emitting phosphors includeCa_(1−x−z)M_(z)S:Eu_(x) where M=Ba, Sr, Mg, Mn and (0<x≤0.2);Ca_(1−x−y)M_(y)Si_(1−z)Al_(1+z)N_(3−z)O_(z):Eu_(x) where M=Sr, Mg, Ce,Mn and (0<x≤0.2); Mg₄Ge_(1−x)O₅F:Mn_(x) where (0<x≤0.2);M_(2−x)Si_(5−y)Al_(y)N_(8−y)O_(y):Eu_(x) where M=Ba, Sr, Ca, Mg, Mn and(0<x≤0.2); Sr_(1−x−y)M_(y)Si_(4−z)Al_(1+z)N_(7−z)O_(z):Eu_(x) whereM=Ba, Ca, Mg, Mn and (0<x≤0.2); and Ca_(1−x−y)M_(y)SiN₂:Eu_(x) whereM=Ba, Sr, Mg, Mn and (0<x≤0.2).

In some embodiments, the phosphor includes portions with inert particlesrather than phosphor, or with phosphor crystals without activatingdopant, such that those portions do not absorb and emit light. Forexample, SiN_(x) may be included as inert particles. The activatingdopant in the ceramic phosphor may also be graded, for example such thatthe phosphors closest to a surface have the highest dopantconcentration. As the distance from the surface increases, the dopantconcentration in the phosphor decreases. The dopant profile may take anyshape including, for example, a linear, step-graded, or a power lawprofile, and may include multiple or no regions of constant dopantconcentration.

Wavelength converter phosphors can be used in conjunction with varioustypes of LEDs. Unconverted light emitted by the LED can be part of thefinal spectrum of light extracted from the structure, though it need notbe. Examples of common combinations include a blue-emitting LED combinedwith a yellow-emitting wavelength converting phosphor, a blue-emittingLED combined with cyan- and red-emitting wavelength converting phosphor,a UV-emitting LED combined with blue- and yellow-emitting wavelengthconverting phosphors, and a UV-emitting LED combined with blue-, cyan-,and red-emitting wavelength converting phosphors. Wavelength convertingphosphors emitting other colors of light may be added to tailor thespectrum of light extracted from the structure.

Binders can be used for holding together and/or attaching wavelengthconverting materials to a substrate. The binders can be organic,inorganic, or organic/inorganic. Organic binders can be, for example,acrylate or nitrocellulose. An organic/inorganic binder can be, forexample, silicone. Silicone can be methyl or phenyl silicone,fluorosilicones, or other suitable high refractive index silicones.Inorganic binders can include sol-gel (e.g., a sol-gel of TEOS or MTMS)or liquid glass (e.g., sodium silicate or potassium silicate), alsoknown as water glass, that have a low viscosity and are able to saturateporous substrates.

In some embodiments binders can include fillers to adjust physical oroptical properties. Fillers can include inorganic nanoparticles, silica,glass particles or fibers, or other materials able to increaserefractive index. In some embodiments, fillers can include materialsthat improve optical performance, materials that encourage scattering,and/or materials that improve thermal performance.

The LED die and wavelength converter may be formed to be square,rectangular, polygonal, hexagonal, circular, elliptical, or any othersuitable shape. In certain embodiments, the wavelength converterphosphor can be a ceramic that can be singulated before positioning nearan LED die, while in other embodiments it can be singulated afterattachment to an LED. The wavelength converter phosphor can be directlyattached to an LED by coating, or alternatively disposed in closeproximity to an LED. For example, it can be separated from an LED by aninorganic layer, a polymer sheet, a thick adhesive layer, a small airgap, or any other suitable structure. The spacing between LED and thewavelength converter phosphor may be, for example, less than 500 micronsin some embodiments or on the order of millimeters in other embodiments.

In examples 1-5 described below, LEDs may comprise a blue emittingsemiconductor diode structure combined with one, two, or more garnetphosphor materials of the general formula[Ce_(x)Lu_(a)Y_((1−a−x))]₃[Ga_(b)Al_((1−b))]₅O₁₂ with 0.01<x<0.06,0<a<1−x, 0<b<0.6, with a first red phosphor material (nitride A) of thegeneral formula (Sr_(c),Eu_(y),Ca_((1−c−y)))AlSiN₃ with 0.001<y<0.02,0.5<c<0.95, and/or with a second red phosphor (“nitride B”) material ofthe general formula Eu_(z),Sr_((1−z))LiAl₃N₄, with 0.003<z<0.015. Thenitride A phosphor material can also be replaced (or combined) with a2-5-8 phosphor material of the general formula[Eu_(y),Ba_(d),Sr_((1−y−d))]₂Si₅N₈, with 0.003<y<0.03, 0.2<d<0.6.

Example 1

FIG. 2A shows the blue, cyan-yellow, and red color points for thisexample on a chromaticity diagram. FIG. 2B shows the emission spectra ofthe blue, cyan-yellow, and red LED groups. In this example, each LED inthe first group (blue color point) comprises a blue emittingsemiconductor diode in combination with the garnet phosphor in siliconewith x=0.02, a=0, b=0.42, using a phosphor mass of 10 percent phosphorof the silicone mass. Each LED in the second group (yellow-cyan colorpoint) comprises a blue emitting semiconductor diode in combination with87% (mass) garnet phosphor with x=0.025, a=1-0.025, b=0, 13% (mass)garnet phosphor with x=0.02, a=0, b=0, Nitride A (99%) with y=0.005,c=0.88, and Nitride B (1%) with z=0.007. The weight ratio of garnets tonitrides=121, with a phosphor mass of 190 percent of the silicone mass.Each LED in the third group (red color point) comprises a blue emittingsemiconductor diode in combination with garnet phosphor with x=0.02,a=0, b=0, Nitride A (83%) with y=0.005, c=0.88, and Nitride B (17%) withz=0.007. The weight ratio of garnets to nitrides=0.52, with a phosphormass of 132 percent of the silicone mass. FIG. 2C shows variation ofFlux and LE with CCT, FIG. 2D shows variation of CCT with drivingcurrent to the blue, cyan-yellow, and red LED groups, and FIG. 2E showsvariation of color rendering parameters Ra and R9 with CCT.Characteristics of the specific LED and phosphor combinations, as wellas other operating characteristics are shown in the table of FIG. 2F.

Example 2

FIG. 3A shows the blue, cyan-yellow, and red color points for thisexample on a chromaticity diagram. FIG. 3B shows the emission spectra ofthe blue, cyan-yellow, and red LED groups. In this example, each LED inthe first group (blue color point) comprises a blue emittingsemiconductor diode in combination with the garnet phosphor in siliconewith x=0.02, a=0, b=0.42, using a phosphor mass of 8.5 percent phosphorof the silicone mass. Each LED in the second group (yellow-cyan colorpoint) comprises a blue emitting semiconductor diode in combination with87% (mass) garnet phosphor with x=0.025, a=1-0.025, b=0, 13% (mass)garnet phosphor with x=0.02, a=0, b=0, Nitride A (99%) with y=0.005,c=0.88, and Nitride B (1%) with z=0.007. The weight ratio of garnets tonitrides=121, with a phosphor mass of 190 percent of the silicone mass.Each LED in the third group (red color point) comprises a blue emittingsemiconductor diode in combination with garnet phosphor with x=0.02,a=0, b=0, Nitride A (83%) with y=0.005, c=0.88, and Nitride B (17%) withz=0.007. The weight ratio of garnets to nitrides=0.07, with a phosphormass of 112 percent of the silicone mass. FIG. 3C shows variation ofFlux and LE with CCT, FIG. 3D shows variation of CCT with drivingcurrent to the blue, cyan-yellow, and red LED groups, and FIG. 3E showsvariation of color rendering parameters Ra and R9 with CCT.Characteristics of the specific LED and phosphor combinations, as wellas other operating characteristics are shown in the table of FIG. 3F.

Example 3

FIG. 4A shows the blue, cyan-yellow, and red color points for thisexample on a chromaticity diagram. FIG. 4B shows the emission spectra ofthe blue, cyan-yellow, and red LED groups. In this example, each LED inthe first group (blue color point) comprises a blue emittingsemiconductor diode in combination with the garnet phosphor in siliconewith x=0.02, a=0, b=0.42, using a phosphor mass of 7.4 percent phosphorof the silicone mass. Each LED in the second group (yellow-cyan colorpoint) comprises a blue emitting semiconductor diode in combination with87% (mass) garnet phosphor with x=0.025, a=1-0.025, b=0, 13% (mass)garnet phosphor with x=0.02, a=0, b=0, Nitride A (99%) with y=0.005,c=0.88, and Nitride B (1%) with z=0.007. The weight ratio of garnets tonitrides=121, with a phosphor mass of 190 percent of the silicone mass.Each LED in the third group (red color point) comprises a blue emittingsemiconductor diode in combination with garnet phosphor with x=0.02,a=0, b=0, Nitride A (83%) with y=0.005, c=0.88, and Nitride B (17%) withz=0.007. The weight ratio of garnets to nitrides=0.07, with a phosphormass of 132 percent of the silicone mass. FIG. 4C shows variation ofFlux and LE with CCT, FIG. 4D shows variation of CCT with drivingcurrent to the blue, cyan-yellow, and red LED groups, and FIG. 4E showsvariation of color rendering parameters Ra and R9 with CCT.Characteristics of the specific LED and phosphor combinations, as wellas other operating characteristics are shown in the table of FIG. 4F.

Example 4

FIG. 5A shows the blue, cyan-yellow, and red color points for thisexample on a chromaticity diagram. FIG. 5B shows the emission spectra ofthe blue, cyan-yellow, and red LED groups. In this example, each LED inthe first group (blue color point) comprises a blue emittingsemiconductor diode in combination with the garnet phosphor in siliconewith x=0.02, a=0, b=0.36, using a phosphor mass of 8 percent phosphor ofthe silicone mass. Each LED in the second group (yellow-cyan colorpoint) comprises a blue emitting semiconductor diode in combination with87% (mass) garnet phosphor with x=0.025, a=1-0.025, b=0, 13% (mass)garnet phosphor with x=0.02, a=0, b=0, Nitride A (99%) with y=0.005,c=0.88. The weight ratio of garnets to nitrides=82.7, with a phosphormass of 189 percent of the silicone mass. Each LED in the third group(red color point) comprises a blue emitting semiconductor diode incombination with garnet phosphor with x=0.02, a=0, b=0, Nitride A (89%)with y=0.005, c=0.88, and Nitride B (11%) with z=0.007. The weight ratioof garnets to nitrides=0.3, with a phosphor mass of 131 percent of thesilicone mass. FIG. 5C shows variation of Flux and LE with CCT, FIG. 5Dshows variation of CCT with driving current to the blue, cyan-yellow,and red LED groups, and FIG. 5E shows variation of color renderingparameters Ra and R9 with CCT. Characteristics of the specific LED andphosphor combinations, as well as other operating characteristics areshown in the table of FIG. 5F.

Example 5

FIG. 6A shows the blue, cyan-yellow, and red color points for thisexample on a chromaticity diagram. FIG. 6B shows the emission spectra ofthe blue, cyan-yellow, and red LED groups. In this example, each LED inthe first group (blue color point) comprises a blue emittingsemiconductor diode in combination with the garnet phosphor in siliconewith x=0.02, a=0, b=0.36, using a phosphor mass of 7.4 percent phosphorof the silicone mass. Each LED in the second group (yellow-cyan colorpoint) comprises a blue emitting semiconductor diode in combination with87% (mass) garnet phosphor with x=0.025, a=1-0.025, b=0, 13% (mass)garnet phosphor with x=0.02, a=0, b=0, Nitride A (99%) with y=0.005,c=0.88, and Nitride B (1%) with z=0.007. The weight ratio of garnets tonitrides=132, with a phosphor mass of 150 percent of the silicone mass.Each LED in the third group (red color point) comprises a blue emittingsemiconductor diode in combination with garnet phosphor with x=0.02,a=0, b=0, Nitride A (83%) with y=0.005, c=0.88, and Nitride B (17%) withz=0.007. The weight ratio of garnets to nitrides=0.58, with a phosphormass of 82 percent of the silicone mass. FIG. 6C shows variation of Fluxand LE with CCT, FIG. 6D shows variation of CCT with driving current tothe blue, cyan-yellow, and red LED groups, and FIG. 6E shows variationof color rendering parameters Ra and R9 with CCT. Characteristics of thespecific LED and phosphor combinations, as well as other operatingcharacteristics are shown in the table of FIG. 6F.

Example 6 and Example 7

In these examples, the blue color point LEDs each comprise a blueemitting semiconductor diode structure combined with a single firstphosphor that absorbs blue light and emits red light, the cyan-yellowcolor point LEDs each comprise a blue emitting semiconductor diodestructure combined with a single second phosphor that absorbs blue lightand emits cyan light, and the red color point LEDs each comprise a blueemitting semiconductor diode structure combined with the first phosphorand with the second phosphor, and no other phosphors.

In Example 6, the semiconductor diode structures emit blue light, thefirst phosphor is Ba_(0.8)Sr_(1.17)Eu_(0.03)Si₅N₈, and the secondphosphor is Y_(2.91)Ce_(0.09)Al_(4.8)Ga_(0.2)O₁₂. FIG. 7A shows theblue, cyan-yellow, and red color points for this example on achromaticity diagram. FIG. 7B shows the emission spectra of the blue,cyan-yellow, and red LED groups. FIG. 7C shows variation of Flux and LEwith CCT, FIG. 7D shows variation of CCT with driving current to theblue, cyan-yellow, and red LED groups, and FIG. 7E shows variation ofcolor rendering parameters Ra and R9 with CCT. Characteristics of thespecific LED and phosphor combinations, as well as other operatingcharacteristics are shown in the table of FIG. 7F.

In Example 7, the semiconductor diode structures emit blue light, thefirst phosphor is Ca_(0.13)Sr_(0.84)Eu_(0.03)AlSiN₃, and the secondphosphor is Lu_(2.94)Ce_(0.06)Al₅O₁₂. FIG. 8A shows the blue,cyan-yellow, and red color points for this example on a chromaticitydiagram. FIG. 8B shows the emission spectra of the blue, cyan-yellow,and red LED groups. FIG. 8C shows variation of Flux and LE with CCT,FIG. 8D shows variation of CCT with driving current to the blue,cyan-yellow, and red LED groups, and FIG. 8E shows variation of colorrendering parameters Ra and R9 with CCT. Characteristics of the specificLED and phosphor combinations, as well as other operatingcharacteristics are shown in the table of FIG. 8F.

This disclosure is illustrative and not limiting. Further modificationswill be apparent to one skilled in the art in light of this disclosureand are intended to fall within the scope of the appended claims.

What is claimed is:
 1. A light emitting device comprising: a first groupof one or more light emitting diodes (“LEDs”) each configured to emitlight having a blue color point in a 1931 International Commission onIlluminations (“CIE”) x,y Chromaticity Diagram, the first group havingan average 1931 CIE x,y color point of x_(blue), y_(blue) withy_(blue)≤0.295; a second group of one or more LEDs each configured toemit light having a cyan or yellow color point in the 1931 CIE x,yChromaticity Diagram, the second group having an average 1931 CIE x,ycolor point of x_(yellow-cyan), y_(yellow-cyan); a third group of one ormore LEDs each configured to emit light having a red color point in the1931 CIE x,y Chromaticity Diagram, the third group having an average1931 CIE x,y color point of x_(red), y_(red); the first group of LEDs,the second group of LEDs, and the third group of LEDs are arranged tocombine light emitted by the LEDs to form a white light output from thelight emitting device;1.10 ≤ (x_(blue) + x_(yellow-cyan) + x_(red)) ≤ 1.40;1.05 ≤ (y_(blue) + y_(yellow-cyan) + y_(red)) ≤ 1.25; each of the LEDsin the first, second, and third groups has a color point for which the xvalue in the 1931 CIE x,y Chromaticity Diagram is greater than 0.15; andeach of the LEDs in the first, second, and third groups has a colorpoint for which the y value in the 1931 CIE x,y Chromaticity Diagram isgreater than 0.15.
 2. The light emitting device of claim 1, wherein:1.15 ≤ (x_(blue) + x_(yellow-cyan) + x_(red)) ≤ 1.40;1.10 ≤ (y_(blue) + y_(yellow-cyan) + y_(red)) ≤ 1.25; each of the LEDsin the first, second, and third groups has a color point for which the xvalue in the 1931 CIE x,y Chromaticity Diagram is greater than 0.2; andeach of the LEDs in the first, second, and third groups has a colorpoint for which the y value in the 1931 CIE x,y Chromaticity Diagram isgreater than 0.2.
 3. The light emitting device of claim 1, wherein:1.20 ≤ (x_(blue) + x_(yellow-cyan) + x_(red)) ≤ 1.32;1.10 ≤ (y_(blue) + y_(yellow-cyan) + y_(red)) ≤ 1.20; each of the LEDsin the first, second, and third groups has a color point for which the xvalue in the 1931 CIE x,y Chromaticity Diagram is greater than 0.2; andeach of the LEDs in the first, second, and third groups has a colorpoint for which the y value in the 1931 CIE x,y Chromaticity Diagram isgreater than 0.2.
 4. The light emitting device of claim 1, wherein thecolor points (x_(blue), y_(blue)), (x_(yellow-cyan), y_(yellow-cyan)),and (x_(red), y_(red)) span an absolute gamut in the CIE 1931 x,yChromaticity Diagram of 0.01<gamut area<0.07.
 5. The light emittingdevice of claim 1, wherein the color points (x_(blue), y_(blue)),(x_(yellow-cyan), y_(yellow-cyan)), and (x_(red), y_(red)) span anabsolute gamut in the CIE 1931 x,y Chromaticity Diagram 0.015<gamutarea<0.055.
 6. The light emitting device of claim 1, wherein the colorpoints (x_(blue), y_(blue)), (x_(yellow-cyan), y_(yellow-cyan)), and(x_(red), y_(red)) span an absolute gamut in the CIE 1931 x,yChromaticity Diagram of 0.02<gamut area<0.045.
 7. The light emittingdevice of claim 1, wherein the blue color point is desaturated.
 8. Thelight emitting device of claim 7, wherein the cyan or yellow color pointis desaturated.
 9. The light emitting device of claim 8, wherein the redcolor point is desaturated.
 10. The light emitting device of claim 1,wherein all of the LEDs in the first group, the second group, and thethird group are phosphor-converted LEDs comprising a semiconductor diodestructure configured to emit blue light and one or more phosphorsarranged to absorb blue light emitted by the semiconductor diodestructure and in response emit light of longer wavelengths.
 11. Thelight emitting device of claim 1, wherein: the LEDs of the first groupeach comprise a semiconductor diode structure configured to emit bluelight and a first phosphor arranged to absorb blue light emitted by thesemiconductor diode structure and in response emit light of a longerwavelength mixed with unabsorbed blue light, and no other phosphors; theLEDs of the second group each comprise a semiconductor diode structureconfigured to emit blue light and a second phosphor arranged to absorbblue light emitted by the semiconductor diode structure and in responseemit light of a longer wavelength, and no other phosphors; and the LEDsof the third group each comprise a semiconductor diode structureconfigured to emit blue light, the first phosphor arranged to absorbblue light emitted by the semiconductor diode structure and in responseemit light of a longer wavelength, and the second phosphor arranged toabsorb blue light emitted by the semiconductor diode structure and inresponse emit light of a longer wavelength, and no other phosphors. 12.The light emitting device of claim 11, wherein: the first phosphorabsorbs blue light and emits red light; and the second phosphor absorbsblue light and emits cyan light.
 13. The light emitting device of claim1, wherein: the LEDs in the first group, the second group, and the thirdgroup are phosphor-converted LEDs comprising a semiconductor diodestructure configured to emit blue light and one or more phosphorsarranged to absorb blue light emitted by the semiconductor diodestructure and in response emit light of longer wavelengths; and thecolor points (x_(blue), y_(blue)), (x_(yellow-cyan), y_(yellow-cyan)),and (x_(red), y_(red)) span an absolute gamut in the CIE 1931 x,yChromaticity Diagram of 0.01<gamut area<0.07.
 14. The light emittingdevice of claim 13, wherein: the LEDs of the first group each comprise afirst phosphor arranged to absorb blue light and in response emit lightof a longer wavelength mixed with unabsorbed blue light, and no otherphosphors; the LEDs of the second group each comprise a second phosphorarranged to absorb blue light and in response emit light of a longerwavelength, and no other phosphors; and the LEDs of the third group eachcomprise the first phosphor arranged to absorb blue light emitted and inresponse emit light of a longer wavelength, and the second phosphorarranged to absorb blue light and in response emit light of a longerwavelength, and no other phosphors.
 15. The light emitting device ofclaim 14, wherein: the first phosphor absorbs blue light and emits redlight; and the second phosphor absorbs blue light and emits cyan light.16. A light emitting device comprising: a first group of one or morelight emitting diodes (“LEDs”) each configured to emit light having ablue color point in a 1931 International Commission on Illuminations(“CIE”) x,y Chromaticity Diagram, the first group having an average 1931CIE x,y color point of x_(blue), y_(blue); a second group of one or moreLEDs each configured to emit light having a cyan or yellow color pointin the 1931 CIE x,y Chromaticity Diagram, the second group having anaverage 1931 CIE x,y color point of x_(yellow-cyan), y_(yellow-cyan)with y_(yellow-cyan)<0.492; a third group of one or more LEDs eachconfigured to emit light having a red color point in the 1931 CIE x,yChromaticity Diagram, the third group having an average 1931 CIE x,ycolor point of x_(red), y_(red); the first group of LEDs, the secondgroup of LEDs, and the third group of LEDs are arranged to combine lightemitted by the LEDs to form a white light output from the light emittingdevice; 1.10 ≤ (x_(blue) + x_(yellow-cyan) + x_(red)) ≤ 1.40;1.05 ≤ (y_(blue) + y_(yellow-cyan) + y_(red)) ≤ 1.25; each of the LEDsin the first, second, and third groups has a color point for which the xvalue in the 1931 CIE x,y Chromaticity Diagram is greater than 0.15; andeach of the LEDs in the first, second, and third groups has a colorpoint for which the y value in the 1931 CIE x,y Chromaticity Diagram isgreater than 0.15.
 17. The light emitting device of claim 1, wherein:1.20 ≤ (x_(blue) + x_(yellow-cyan) + x_(red)) ≤ 1.32;1.10 ≤ (y_(blue) + y_(yellow-cyan) + y_(red)) ≤ 1.20; each of the LEDsin the first, second, and third groups has a color point for which the xvalue in the 1931 CIE x,y Chromaticity Diagram is greater than 0.2; andeach of the LEDs in the first, second, and third groups has a colorpoint for which the y value in the 1931 CIE x,y Chromaticity Diagram isgreater than 0.2.
 18. The light emitting device of claim 1, wherein thecolor points (x_(blue), y_(blue)), (x_(yellow-cyan), y_(yellow-cyan)),and (x_(red), y_(red)) span an absolute gamut in the CIE 1931 x,yChromaticity Diagram of 0.01<gamut area<0.07.
 19. The light emittingdevice of claim 1, wherein the color points (x_(blue), y_(blue)),(x_(yellow-cyan), y_(yellow-cyan)), and (x_(red), y_(red)) span anabsolute gamut in the CIE 1931 x,y Chromaticity Diagram 0.015<gamutarea<0.055.
 20. The light emitting device of claim 1, wherein the colorpoints (x_(blue), y_(blue)), (x_(yellow-cyan), y_(yellow-cyan)), and(x_(red), y_(red)) span an absolute gamut in the CIE 1931 x,yChromaticity Diagram of 0.02<gamut area<0.045.